Meeting Abstract
P3.71 Monday, Jan. 6 15:30 The Influence of Environmental Temperature on Heat Dissipation in Hummingbirds LANGLAND, KM*; POWERS, DR; WETHINGTON, SM; George Fox Univ., Newberg, OR; George Fox Univ., Newberg, OR; Hummingbird Monitoring Network, Patagonia, AZ klangland11@georgefox.edu
Hummingbirds in landscapes warming due to climate change will have greater need to dissipate excess heat. Elevated environmental temperatures could result in surface temperature (Ts) exceeding body temperature (Tb) due to increased radiative heat gain. This would favor net heat gain due to a reversal of the thermal gradient. Heat dissipation across body surfaces requires a gradient where Tb > Ts. In this study we determine how changes in Ts, over a range of operative temperatures (Te) on hummingbird landscapes might influence this thermal gradient and thus the ability of the hummingbird to dissipate excess heat. We measured Ts of shaded perched broad-billed hummingbirds (Cynanthus latirostris; ~ 3.2 g) by infrared thermography (FLIR SC6700). Ts was positively correlated with Te (R2= 0.96, P < 0.0001). As Ts approaches Tb (assumed ~41-42 °C), the thermal gradient becomes smaller and passive heat dissipation is limited. At high Te (> 45 °C), Ts = ~42°C similar to our presumed Tb minimizing any thermal gradient between the body core and surface. While we have no measurements at Te > 47 °C we frequently observed hummingbirds panting at times when Te was high (sometimes > 50 °C) suggesting that reversal of the thermal gradient might have occurred. Ts of hummingbirds perched for an extended period of time (> 60s) increased linearly with time regardless of Te suggesting that body surfaces are perhaps convectively cooled during flight before perching. Our data suggests that infrared thermography might be a good tool for identifying critical Tes at which thermoregulation becomes difficult due to the inability to passively cool. Such information is important in our efforts to understand organismal response to warming environmental temperatures associated with climate change.
